Facebook Says Technical Flaw Exposed 6 Million Users

SAN FRANCISCO — Facebook has inadvertently exposed six million users’ phone numbers and e-mail addresses to unauthorized viewers over the last year, the company said late Friday.

Facebook blamed the data leaks, which began in 2012, on a technical flaw in its huge archive of contact information collected from its 1.1 billion users worldwide. As a result of the problem, Facebook users who downloaded contact data for their list of friends obtained additional information that they were not supposed to have.

Facebook’s security team was alerted to the problem last week and fixed it within 24 hours. But Facebook did not publicly acknowledge the flaw until Friday afternoon, when it published a message on its blog explaining the situation.

A Facebook spokesman said the delay was because of a company procedure stipulating that regulators and affected users be notified before making a public announcement.

“We currently have no evidence that this bug has been exploited maliciously, and we have not received complaints from users or seen anomalous behavior on the tool or site to suggest wrongdoing,” Facebook said on its blog.

While the privacy breach was limited, “It’s still something we’re upset and embarrassed by, and we’ll work doubly hard to make sure nothing like this happens again,” it added.

The breach follows recent disclosures that several consumer Internet companies, including Facebook, Google, Microsoft, Apple and Yahoo, turned over troves of user data to a large-scale electronic surveillance program run by American intelligence officials.

The companies, led by Facebook, successfully negotiated with the United States government last week to reveal the approximate number of user information requests that each company had received, including secret national security orders.

A version of this article appears in print on , on Page B4 of the New York edition with the headline: Facebook Says Technical Flaw Exposed 6 Million Users. Order Reprints | Today’s Paper | Subscribe